This invention relates generally, as indicated, to a piston rod assembly, the piston head of which is made separately from the piston rod and subsequently bonded thereto. Also, this invention relates to a method of fabricating such piston rod assembly.
Making the piston head and rod separately not only facilitates their fabrication, but permits them to be made out of different materials. This is particularly advantageous in applications where, for example, it is desired to make the rod out of relatively high strength-to-weight fibrous composite materials for reduced weight, as when the piston rod assembly is part of a fluid actuator used in flight controls for high performance aircraft and the like.
Also, making the piston rod (as well as the cylinder walls) of the actuator out of fibrous composite materials would be desirable in applications where ballistic tolerance is an objective because of the frangibility of such materials. Composites are relatively brittle and tend to fragment when impacted, thus causing very little tendency to jam. Accordingly, if two or more hydraulic actuators are connected in parallel, and the composite piston rod of one of the actuators is struck by a ballistic projectle, it will not jam and thus prevent the other actuator(s) from functioning.
Such a piston rod assembly should be of a relatively low cost, envelope efficient design. Also, if the rod is made of composite materials, a suitable barrier impermeable to hydraulic fluid and a durable wear surface should be provided over the exposed surface of the rod. In addition, the joint between the piston head and rod should be able to withstand the stresses incurred during use of the actuator. Furthermore, an efficient method of assembling the piston head onto the rod and securing same thereto should be provided.